The invention relates to transporting a civil engineering structure in an aquatic medium.
For simplicity, it is common to transport a civil engineering structure by sea that is not in its finished state but is in the form of separate elements which are then assembled at sea into said civil engineering structure.
One example of such a civil engineering structure is a wind turbine. In its final assembled state, a wind turbine generally comprises a mast with a nacelle mounted on top which cooperates with a rotor accepting multiple blades.
Operations are performed to assemble the various component elements of the wind turbine into this final state.
These operations are generally complex and costly.
Such is particularly the case for the mounting of and the nacelle which is very heavy and of the blades.
This is explained by the fact that the blades are cumbersome and they have a high point of attachment on the wind turbine.
The assembly is conventionally done by first attaching some or all of the blades onto the rotor and then raising the “rotor+blades” assembly to the top of the vertically positioned mast. The lifting means necessary for this purpose, for example cranes, are heavy and complex to use.
The situation is particularly difficult for an offshore wind turbine, intended for placement in the open sea.
It is indeed usual to transport the component elements of such a wind turbine separately, then assemble them at sea.
This type of wind turbine is generally assembled as follows: the base, the mast, and if applicable the metal shaft section of the wind turbine are constructed on land, then are transported by sea while held by a crane placed on a barge, and then, once at sea, the rotor and the blades are installed on the mast to form the rotating part of the wind turbine.
Usually the rotor and mast are transported separately by sea on a transport ship. The three blades (or only two of the three blades to reduce space requirements when stored on the transport ship) are already attached to the rotor during transport. Once at sea, the rotor and the blades are lifted together for placement at the top of the mast, using cranes mounted on barges or on fixed platforms.
Such maritime assembly is relatively long, complex, and costly.
In addition, the level of safety is sometimes lower than for work on land.
Even if transporting a finished civil engineering structure by sea was envisaged, for example by completely supporting it on a boat or barge, complex work would still need to be performed at sea in order to install the civil engineering structure in its final position.
When a wind turbine is transported on its side on a barge, its installation at sea requires lifting it with a crane and raising it to the vertical for placement in its final position. Such maritime work is relatively long, complex, and costly to perform.
An object of the invention is to reduce at least some of these disadvantages.